The universal nature of gravity together with the strict consistency
requirements that graviton scattering obeys make such an assertion
plausible. It is a well-known fact that scattering of massless
spinning particles is very
constrained [1]}. In fact, massless particles of
spin larger than two do not admit a non-trivial
\(S\) -matrix [2]}. Gravitons, being massless spin-two
particles, are thus expected to have an especially constrained
\(S\) -matrix, and the assertion made in the previous paragraph is thus
particularly plausible for graviton scattering which is the subject of
the present paper.
